The pelvis after surgery for rectal carcinoma: serial CT observations with emphasis on nonneoplastic features.

Ten asymptomatic patients who had undergone resection of rectal carcinoma were evaluated prospectively by at least three serial computed tomographic (CT) examinations of the pelvis within 24 months of surgery. Of the seven patients who had undergone abdominoperineal resection, five were found to have a presacral mass due to normal postoperative changes within the first 4 months. The mass showed a variable diminution between 4 and 9 months after operation and developed a more distinct outline, partial separation from the sacrum, or a change in configuration to a thin transverse sliver. These changes indicate the possibility of CT differentiation of a normal postoperative mass from local recurrence. In the other five patients, no postoperative mass was observed. In one patient CT demonstrated a solitary 1.5 cm lymph node metastasis. This patient was asymptomatic and had a normal carcinoembryonic antigen level. From these observations, a baseline CT study of the pelvis within 2-4 months of resection of rectal carcinoma, followed by serial CT examinations at about 6-month intervals is recommended for the detection of early asymptomatic pelvic recurrence and to facilitate differentiation from persistent postoperative changes.